Nano Cerium Oxide, Iron Particle Composition As The Tribological Properties Of Lubricating Oil Additives And Mechanism

With the high speed of development of industrial society, requirements to lubricating oils and their additives are expanding continuously, and the capability requirements of these oils are also increasing. The applications of ordinary inorganic particles are restricted by their dispersing performance. It is known that the traditional oil-soluble anti-wear and friction-reducing additives always produce the environment pollution, though they can increase load-carrying abilities and extreme pressure properties of lubricating oil to a certain degree. Today, the application of nano-materials in lubrication provides a new option. The characterization, tribological performance and mechanism of anti-wear and friction reduction of nano-particles of CeO₂ and Fe are studied in this paper. The main conclusions are reached as follows.1. The shapes and average sizes of nano-particles of CeO₂ and Fe have been measured by TEM. The results indicate that both nano-particles of CeO₂ and Fe appear as spherical particles, and their diameters are about 10.4nm and 45nm .respectively.2. Tribological performances of nano-particles of CeO₂ and Fe as lubricating oil additives were tested in the friction and wear test machine. The results indicate that good dispersion and stability of nano-particles are key factors to use them as lubricating oil additives. Only with evenly-distributed nanoparticles can the excellent function of anti-wear and friction reduction be achieved.3. The optimal proportion of nano-particles of CeO₂ and Fe is:Wt_CeO2% :Wt_Fe %=1:1, and the total content Wt_(CeO2+Fe)% is about 0.6%.4. Through the study of the tribological performonces of nano-particles of CeO₂ and Fe, the mechanism of anti-wear and friction reduction were discussed. And individual opinions can been proposed as follows.(1)"tiny polishing": When the machine start to run, Nano-particles of CeO₂ or Fe will polish the micro gibbosity. It makes the friction surface more flatness, so it can reduce the friction factor and the wear value.(2) Nano-particles of CeO₂ and Fe have different functions on the friction surface, CeO₂ nano-particles work similar to "tiny ball bearing", which can support loads; and Fe nano-particle can fill in and repair worn surfaces.(3)Only with appropriate proportion, can nano-particles of CeO₂ and Fe give fully play to properties of anti-wear and friction reduction. When both nano-particles of CeO₂ and Fe are added in the lubricating oil, more CeO₂ nano-particles work similar to "tiny ball bearing", which can mostly support loads; on the contrary, more Fe nano-particles mostly fill in and repair worn surfaces. These two nano-particles alone give neither full play nor co-operating play to properties of anti-wear and friction reduction. In our research, when Wt_CeO2:Wt_Fe=1:1, CeO₂ nano-particles work as "tiny ball bearing" on the surface that filled by Fe nano-particle, they give full play to properties of anti-wear and friction reduction.The present study is a part of "Study on key technology of industry application of nanoparticles additives of lubricating oils" (05FZ31) of science and technology project of Shanghai Educational Committee. More researches are expectably to be further developed.